Preparation of methylolated carbamates



United States Patent ice 3,391,181 PREPARATION OF METHYLOLATEDCARBAMATES Donald R. Schenerl, Franklin Lakes, N.J., assignor to .l'. P.Stevens 81 Co., Inc., New York, N.Y., a corporation of Delaware NoDrawing. Filed Mar. 13, 1965, Ser. No. 440,938 5 Claims. (Cl. 260-482)ABSTRACT OF THE DISCLOSURE A method of preparing dimethylolatedaliphatic carbomates in improved yield and substantially free from bothmonomethylolated contaminant and formaldehyde, comprising the steps of(l) Admixing an essentially anhydrous reaction mixture of alkylcarbamate containing at least two methylolatable amido hydrogensselected from the group consisting of monoalkyl carbamates and alkylenebis-carbamates, paraformaldehyde in an amount corresponding to fromabout 0.9 to about 1.1 equivalent weight of paraformaldehyde for eachamido hydrogen atom in said carbamates, and sufiicient basic catalyst tomaintain the pH from about 8.0 to about 11.0 during the reaction, and

(2) Heating the reaction mixture between about 50 C.to about 85 C. untila substantial quantity of dirnethylolated product is produced andisolating the product contained therein.

This invention relates to an improved method for preparing finishingagents for cellulosic textile fabrics. More particularly, it relates tothe preparation of methylol carbomates.

Cellulosic textile fabrics can be treated with cross-linking agents inorder to impart to such fabrics enhanced wrinkle resistance and improvedsmooth drying after laundering. Among the cross-linking agents whichhave been demonstrated to be effective are methylolated carbamates whichare usually prepared by reacting an organic carbamate with aqueousformaldehyde in an alkaline medium. In this methylolation reaction, theamido hydrogen atoms of the carbamate are replaced by methylol groups.In order to obtain cross-linking of the cellulosic fabric treated withthe carbamate, it is necessary that the methylolated carbamates containtwo or more reactive mcthylol groups. It has been found, however, thatthe preparation of dimethylolated carbamates by aqueous formaldehydetreatment is usually unsatisfactory in that the yield of the dimethylolcompound is lowered by the incomplete conversion of the monomethylolcompound to the dimethylol carbamate, with the result that mixtures ofthe monomethylol and dimethylol compounds are obtained. It has beennecessary, consequently, to react excess formaldehyde with the carbamatein order to drive the methylolation reaction further to completion.

The use of excess formaldehyde in methylolation reactions presentsserious processing shortcomings. The presence of free (i.e., unbound)formaldehyde, a serious irritant, in the reaction mixture presents asafety hazard not only to the personnel running the reaction, but alsoto personnel subsequently using the reaction product in the treatment oftextile materials. Moreover, t .e use of large amounts of formaldehydeinevitably results in waste of the reagent. Further, the presence offree formaldehyde may cause variations in the properties of treatedcellulosic textiles due to undesirable side reactions between theformaldehyde and cellulose. Lastly, the utilization of aqueous reactionmixtures increases the cost of preparing, handling, and shipping themethylolated materials.

In addition to the failings outlined above, methods em- 3,391,181Patented July 2, 1968 ploying aqueous formaldehyde solutions exhibit afurther disadvantage. Even though excess equivalents of formaldehyde areused in the reaction, the conversion of a carbamate to a dimethylolatedcompound is seldom substantially complete. If the reaction product ratiois expressed as the number of moles of bound formaldehyde per mole ofcarbamate nitrogen, a CH O/ N ratio of 2.0 corresponds to completeconversion to N, N-dimethylol alkyl carbamate, and a CHQO/ N ratio of1.0 represents N-methylol alkyl carbamate. It has been found that use ofexactly 2 moles of formaldehyde solution (the stoichiometric amount) inthe methylolation reactions hitherto used yields a product having a CHO/N ratio of from 1.3 to 1.5, rather than the theoretical value of 2.0.

It is an object of this invention to provide a method for theessentially anhydrous preparation of N-methyh olated carbamates.

Another object of this invention is to provide a safe, economical, andeffective method for preparing N-methylolated carbamates, saidcarbamates subsequently being used in the cross-linking of cellulosictextiles.

A further object of this invention is to provide a reaction forpreparing mixtures of N-methylol and N, N- dimethylol carbamates whereina major amount of N- methylol carbamate is converted to N, N-dimethylolcarbamate.

Other objects and the advantages of this invention will be apparent fromthe description that follows hereinafter.

In accordance with this invention, an alkyl carbamate is reacted withparaforrnaldehyde under basic conditions to yield the correspondingN-methylolated carbamate. This reaction may be carried out underessentially anhydrous conditions, and thereby circumvents theundesirable features characteristic of prior art methods utilizingaqueous formaldehyde treatment.

Exemplary of the carbarnates which may be used in the process of thisinvention are those compounds represented by the formula wherein R ishydrogen; R may be hydrogen, straight or branched chain-lower alkylhaving from 1 to 4 carbon atoms; X may be alkylene having up to 20carbon or an ethylenically unsaturated group having from 3 to 6 carbonatoms, such as, e.g., CH=CH-CH or the residue of a branched chain alkylgroup having up to 20 carbon atoms; and Z may the hydrogen, halogen,alkoxy,

i -o- N\ where R and R are as defined above. Also suitable for use inthis invention are biscarbamates of primary diamines represented by theformula if t t i R3OCN-X-N-CO-Rs wherein R is a straight or branchedchain-lower alkyl group having from 1 to 4 carbon atoms and X is asdefined above.

As was mentioned previously, the methylolation reaction of thisinvention is carried out under basic conditions which may be attained byuse or" such basic catalysts as the hydroxides of the alkali andalkaline earth metals, and preferably sodium hydroxide. Sufiicientamounts of catalyst are used to maintain the pH of the reaction fromabout 8 to about 11, with the preferred range being from 9.5 to 10.5.

The temperature at which the reaction proceeds may vary within a widerange, e.g., from about C. to about 100 C. It is preferred, however, tomaintain the reaction temperature from 50 C. to 85 C. in order tominimize side reactions and achieve rapid reaction. The duration ofheating is not critical and can vary within wide limits, e.g., from 10minutes to 10 hours. The preferred reaction time, however, is about 2hours.

The amount of paraforrnaldehyde to be employed in the process of thisinvention will be determined by the degree of conversion desired, aswell as by the number of amide hydrogen atoms present in the earbamate.It is preferred to employ one equivalent weight of paraformaldehyde foreach amide hydrogen present in the earbamate, although the ratio ofparaformaldehyde to amide hydrogen may range from about 0.9 to about1.1. The use of stoichiometric quantities of paraformaldehyde in thisinvention will give a substantial yield of dimethylol carbamate, so thatan excess amount of paraforrnaldehyde serves no purpose.

In carrying out the process of this invention, anhydrous conditions oressentially anhydrous conditions can be used. In one embodiment of theprocess, the dry ingredients are charged to a suitable reactor, thecatalyst added, and the mixture is heated. The mixture becomes fluid andstirrable at a temperature of from to C. and is thereafter stirred atthe desired elevated temperature for from about 2 to about 4 hours. Ifless than substantially complete conversion is desired, the time ofheating may be reduced accordingly. In another embodiment of thisinvention, a low melting carbamate, e.g., ethyl carbamate (melting pointC.) may be melted hefore addition thereto of paraformaldehyde and thebasic catalyst. The mixture remains fluid after addition of theparaformaldehyde and catalyst and may be stirred. Alternatively, smallamounts of water may be added to assist in fluidizing the reactionmixture. However, the process of this invention eliminates the necessityof using even slight amounts of water in the reaction and consequentlyavoids the disadvantages inherent in such usage.

The N,N-dimethylolated alkyl carbamates produced by the process of thisinvention are stable indefinitely. These carbamates may also be useddirectly after preparation or the reaction mixture may be neutralizedwith an acid to a pH of from about 6.5 to about 7.5 and subsequentlystored.

The methylolated carbamates of this invention may be applied tocellulosic textiles by any of the conventional means known to thepractitioner. Using these carbamates, cross-linked textiles are obtainedwhich exhibit enhanced smooth drying after laundering and goodresistance to wrinkling.

In summary, then, the process of this invention enables carbamates to bemethylolated without the use of aqueous formaldehyde solutions.Accordingly, the hazards, as well as the expense, of employing theseaqueous solutions have been effectively circumvented. At the same time,the process of this invention yields carbamates having an increaseddegree of methylolation. As was mentioned previously, these carbamatesfind widespread application in the cross-linking of cellulosic textiles.

The following examples will further illustrate the embodiments of thisinvention. All parts given are by weight unless otherwise indicated.

Example 1 N,N-dimethylol ethyl carbamate was prepared by reaction of 178grams ethyl carbamate (2 moles) with grams paraformaldehyde (4 moles)using 1 gram of 50% aqueous sodium hydroxide as catalyst. The mixturewas agitated and heated slowly starting at 25 C. When the temperaturereached 27 C. a fiuid slurry was ob tained which cleared at 65 C. Thereaction mixture was held at 6570 C. for 5 hours, after which time thepH thereof was about 10.2. On standing overnight the product was foundto contain 4.8% free formaldehyde and 40.06% total formaldehyde(theoretical=40.1% representing a CH O/N ratio of 1.76.

Example 2 N,N-dimethylol ethyl carbamate was prepared by melting 1780grams ethyl carbamate (20 moles) and adding to this at 53 C. 1200 gramsof paraformaldehyde (40 moles). To this fluid slurry were charged 10grams aque ous 50% sodium hydroxide. An immediate temperature increasewas observed from 5367 C. in 3 minutes. The reaction mixture was held at6466 C. for 3 hours and a portion neutralized to pH 7.1 withconcentrated 37% hydrochloric acid. The pH of the mixture beforeneutralization was about 10.1. The neutralized product was found tocontain 4.56% free formaldehyde, which corresponds to a CH O/N ratio of1.77. The remaining portion of the reaction was found to contain 4.2%free formaldehyde after standing for 3 days which corresponds to a CHO/N ratio of 1.79.

Example 3 N,N-dimethylol methyl carbamate was prepared by reaction ofgrams methyl carbamate (2 moles) with 120 grams of paraformaldehyde (4moles) using 1.0 gram of 50% aqueous sodium hydroxide as catalyst. Themixture was agitated and heated slowly starting at 26 C. When thetemperature reached 33 C., a fluid slurry was obtained which was clearat 68 C. The reaction mixture was held at 60-68 C. for 3 hours and thencooled. Neutralization to a pH of 7.12 was carried out using 1 gram of37% hydrochloric acid. The pH of the mixture before neutralization wasabout 10. The product was found to contain 7.3% free formaldehyde, whichcorresponds to a CH O/N ratio of 1.67.

Example 4 N,N-din1ethylo1 methylene bis (ethyl carbamate) was preparedby reaction of grams of methylene bis (ethyl carbamate) (1 mole) with 60grams of paraformaldehyde (2 moles) using 1.0 gram of 50% aqueous sodiumhydroxide as catalyst. The mixture was agitated and heated slowlystarting at 25 C. When the temperature reached 48 C., a fluid slurry wasobtained which became clear at 65 C. The reaction mixture was held at65-73 C. for 3 hours, after which time the pH of the mixture was about9.5. The reaction was allowed to cool overnight and Was found to contain4.9% free formaldehyde, which corresponds to a CH O/N ratio of 1.59.

Example 5 This example illustrates the superior results obtained whenthe process of the present invention is employed rather than a prior artprocess.

The method set forth in Examples 14 was followed in preparingFormulations 2, 3 and 5, whereas Formulations 1 and 4 were preparedaccording to an exemplary prior art method. In carrying out the priorart technique, a 30% aqueous solution of a carbamate in formaldehyde wasprepared by dissolving the carbamate in 4 times its weight of water andthen adding sufiicient 37% formaldehyde solution to afford a ratio offormaldehyde to the carbamate of 2:1. The reactants, their ratio, andthe CH O/N ratio present in the final product are set forth in the tablebelow.

formaldehyde (2).

From the results presented hereinabove, it can be seen that the productof the present invention contains a significantly higher proportion ofthe dimethylolatcd compound.

Example 6 N,N-dimethylol allyl carbamate was prepared by reaction of50.5 grams of allyl carbamate (0.5 mole) with 30 grams ofparaformaldehyde (1 mole) using 0.25 gram of 50% aqueous sodiumhydroxide as catalyst. The mixture was agitated and heated slowly,starting at 24 C. The temperature rose exothermically to 33 C., and themixture was heated to 60 C. at which point it cleared. It was held at 60C. for two hours, and was found to contain 7.45% free formaldehyde. Thereaction mixture was cooled and filtered to yield a clear water-whiteviscous liquid. The CH O/N ratio based on free formaldehyde analysis was1.60.

Example 7 N,N-dimethylol 2-ethylhexyl carbamate was prepared by reactionof 52 grams of Z-ethylhexyl carbamate (0.3 mole) with 18 grams ofparaformaldehyde (0.6 mole) using 0.25 grams of 50% aqueous sodiumhydroxide as catalyst. The mixture was heated to 80 C. and was clear atthis temperature. The reaction mixture was held at 6070 C. for two hoursand cooled, whereupon a viscous oil was obtained which showed 3.6% fereformaldehyde, corresponding to a CH O/ N ratio of 1.72.

Example 8 N,N-dimethylol cetyl stearyl carbamate (this carbamate isactually an equimolar mixture of cetyl carbamate and stearyl carbamate)was prepared by reaction of 60 grams of cetyl stearyl carbamate with 12grams of paraformaldehyde, using 0.25 gram of 50% aqueous sodiumhydroxide as catalyst. The mixture was initially heated to 60 C. and, onfurther heating to 80 C., gave a clear liquid. The reaction mixture washeld for two hours at 80 C. and cooled. A solid white product wasobtained which showed 3.3% free formaldehyde, corresponding to a CH O/Nratio of 1.60.

Example 9 N,N-dimethylol 2-chloroethyl carbamate was prepared by thereaction of 49.2 grams of 2-chloroethyl carbamate (0.4 mole) with 24.0grams of paraformaldehyde (0.8 mole) using 0.2 gram of 50% aqueoussodium hydroxide as catalyst. The mixture was heated to 50 C. withstirring. It was held at this temperature for one hour where- 6 upon aproduct having a CH O/N ratio of 1.70 was obtained.

Example 10 N,N-dimethylol 2-methoxyethyl carbamate was prepared byreaction of 143.0 grams of Z-methoxyethyl carbamate (1.2 moles) with 72grams of paraformaldehyde (2.4 moles) using 0.25 gram of aqueous sodiumhydroxide as catalyst. The mixture was agitated and heated for one hourat -65 C. The reaction mixture was cooled to room temperature and foundto contain 5.85% free formaldehyde. The CH O/N ratio of the productbased on free formaldehyde analysis was 1.66.

Any departure from the above description which conforms to the presentinvention is intended to be included within the scope of the inventionas defined by the following claims.

What is claimed is: 1. A method of preparing dimethylolated aliphaticcarbamates in improved yield and substantially free from bothmonomethylolated contaminant and formaldehyde, comprising the steps of(1) admixing an essentially anhydrous reaction mixture of alkylcarbamate containing at least two methylolatable amido hydrogensselected from the group consisting of monoalkyl carbamates and alkylenebiscarbarnates, paraformaldehyde in an amount corresponding to fromabout 0.9 to about 1.1 equivalent weight of paraformaldehyde for eachamido hydrogen atom in said carbamates, and sufiicient basic catalyst tomaintain the pH from about 8.0 to about 11.0 during the reaction, and

(2) heating the reaction mixture between about 50 C.

to about C. until a substantial quantity of dimethylolated product isproduced and isolating the product contained therein.

2. The method of claim 1 wherein said basic catalyst is selected fromthe group consisting of alkali metal hy droxides and alkaline earthmetal hydroxides, the pH is maintained between about 9.5 and 10.5, andthe reaction time varies between about 2 to about 5 hours.

3. The method of claim 2 wherein the carbamate used is a monoalkylcarbamate.

4. The method of claim 3 wherein the monoalkyl carbamate is selectedfrom the group consisting of ethyl carbamate, methyl carbamate,Z-ethylhexyl carbamate, cetyl stearyl carbamate, 2-chloroethylcarbamate, Z-methoxyethyl carbamate and 'alkyl carbamate.

5. The method of claim 1 wherein the bis alkyl carbamate is methylenebis(ethyl carbamate).

References Cited UNITED STATES PATENTS 2,297,531 9/1942 Bock 260-5842,760,977 8/1956 Fener et a1. 260-561 2,864,861 12/1958 W-ohnsiedler260561 3,144,299 8/1964 Frick et a1. 3,226,428 12/1965 Vail et a1.260-482 LORRAINE A. WEINBERGER, Primary Examiner.

A. P. HALLUIN, Assistant Examiner.

